ISO INTERNATIONAL STANDARD 8889 First edition 1988-02-01 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXKAYHAPOAHAR OPTAHM3ALMR O CTAHAAPTM3ALMM Chromium ores and concentrates -- Determination of aluminium content --- Complexometric method Minerais et concentres de chrome -- Dosage de I'aluminium -- Methode complexometrique Reference number ISO 8889: 1988 (E) Not for Resale Foreword Iso (the International Organization for Standardization) is a worldwide federation of national standards bodies (iso member bodies). The work of preparing tnternational Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with IsO, also take part in the work. Draft internationat Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISo Council. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard iSO 8889 was prepared by Technical Committee ISO/TC 65, Manganese and chromium ores. Users shoud note that all International Standards undergo revision from time to time and that any reference made herein to any other International Standard implies its latest edition, unless otherwise stated. @ International Organization for Standardization, 1988 Printed in Switzerland working permitted without license from IHS Not for Resale ISO 8889 : 1988 (E) INTERNATIONAL STANDARD Chromium ores and concentrates - Determination of aluminium content - Complexometric method Scope and field of application 4.4 Nitric acid, 1,40 g/ml. This International Standard specifies a complexometric method 4.5 Hydrofluoric acid, 40 %.(m/ m) solution. for the determination of the aluminium content of chromium ores and concentrates. The method is applicable to a concen- Perchloric acid, @ 1,50 g/ml. 4.6 tration range of 1,5 to 20,0 % (m/m) of aluminium content in chromium ores. 4.7 Sulfuric acid, g 1,84 g/ml, diluted 1 + 1. It should be read in conjuction with ISo 6629 4.8 Ammonia solution, Q 0,91 g/ml, diluted 1 + 1. 2 Reference 4.9 Sodium hydroxide, 20 % (m/m) solution. IsO 6629, Chromium ores and concentrates Methods of chemical analysis - General instructions. Sodium hydroxide, 1 % (m/m) solution. 4.10 Principle 4.11 Sodium disulfate (pyrosuifate, Na2S207). Decomposition of a test portion by treatment with perchloric, 4.12 Ammonium chioride, 2 % (m/m) solution with addi- nitric and hydrochloric acids with removal of the chromium by tion of ammonia solution to adjust the pH to 7,0 to 8,0. distillation as chromyl chloride. Separation of the insoluble residue, the filtrate being reserved as the main solution. Phenolphthalein indicator, 10 g/l alcoholic solution. 4.13 Ignition of the residue and treatment with sulfuric and Dissolve 1 g of indicator in 100 ml of ethanol, 60 % (m/m) hydrofluoric acids. Fusion of the ignited residue with sodium solution. disuifate. Dissolution of the melt and combination of the solu- tion obtained with the main solution. 4.14 Sodium fluoride, 4 % (m/m) solution. Precipitation of the hydroxides with the ammonia solution filtration and redissolution of the hydroxides in hydrochloric Store in a polyethylene bottle. acid. Reduction of chromate ions to ions of Cr(lll) with hydrogen peroxide. Separation of aluminium from iron and 4.15 Buffer solution, pH 5,5 to 5,9. other elements with sodium hydroxide. Dissolve 500 g of the ammonium acetate in 1 000 ml of water, Addition of EDTA Na2 solution to an aliquot portion of the add 30 ml of acetic acid (g 1,054 9 g/ml) and mix. solution. Titration of an excess of EDTA Na2 with zinc acetate solution, using xylenol orange as an indicator. Decomposition Check